Perchloroethylene and trichloroethylene, two solvents commonly used in drycleaning, are highly toxic and hence the leakage of such solvents into the environment from a drycleaning plant may prove to be undesirable. In addition it is advantageous to detect the concentration of the solvent in the airstream used within the drycleaning machine or to establish the level of the solvent in air released from the drycleaning machine. To this end it has been found to be advantageous to monitor the level of perchloroethylene or trichloroethylene in association with a drycleaning plant.
The expression "monitoring the solvent content of the air" is used herein to refer to several alternatives. For example, it may involve determining whether the solvent content of the air exceeds a predetermined level. Alternatively, it may involve a measurement of the level of solvent content in the air. Finally, it may involve a determination as to whether or not the air contains traces of solvent. Each of these conditions and any combination thereof are referred to collectively as a monitoring of the solvent content.
To establish the solvent content of air, there have been two techniques which have been employed heretofore. In the first of these techniques, a sampling tube is used to quantitatively determine the solvent content of the air by a sampling technique which cannot be carried out continuously. In the second approach a halogen test lamp is used and is effective to establish whether or not the air contains solvent, but is not effective for a continuous determination of the level of the solvent in the air. Consequently, notwithstanding the fact that environmental protection laws require that solvent concentration in the region of a drycleaning plant be maintained below a certain level, there has been no effective way heretofore, to the knowledge of applicant, to provide a continuous monitoring of the solvent content of the air in all of the three respects mentioned previously.